Electrode sealing-in



u Sept. 24, 1940. G. A. FREEMAN 2,215,641

ELECTRODE SEALING IN Filed NOV. 25, 1938 'lill/111111111110711 INVENTOR '6. A FREE/*1,9m f BY f 15 l LGS Am hwL ATTORNEY.

oxidization of electrodes Patented Sept. 214, 19.40

PATENT OFFICE ELECTRODE SEALING-IN George A. Freeman, East Orange, N. J., assignor of Pennsylvania to Westinghouse' Electric `& Manufacturing Company, East Pittsburgh, Pa., a corporation Application November z5, 193s, serial No. 242,178

2Claims.

My invention relates to electrodes and especially to the sealing in of such electrodes in lamps requiring application of high temperatures.

An object of my ,invention is to prevent the while they are being sealed in the casing. Y

Other objects and advantages of the invention will be apparent from the following description and drawing, in which:

Fig. 1 is an elevation of a lathe in which my invention has been incorporated.

Fig. 2 is an enlarged cross-sectional view of the pressure release mechanism of Fig. 1. i

Fig. 3 is a view mainly in cross section of the chuck and lamp apparatus illustrating one of the rst steps inthe formation of a quartz lamp according to my invention.

Figs. 4 and 5 are views mainly' in cross-section of the tube and adjacent jaws of the chucks illustrating the formation of oneend of the seal of the lamp. y Fig. 6 is a view mainly in cross section of the lamp and adjacent jaws of the chucks illustrating the method of forming the seal about the other end of the quartz lamp.

Fig. 7 is a view in elevation of the completed- A in View of the resulting oxidization. Pure nitrogen has been utilized as an atmosphere in which to seal-in the tubes but methods heretofore utilized have not satisfactorily applied the nitrogen atmosphere to the lamp. It is necessary, of course, that the nitrogen not interfere with the application of the iiame and the heat therefrom to the outside of the casing.. It is further important that the nitrogen be regulated so that it has the desired low pressure within the tube while the seal is being formed and then increased pressure when the seal has been sufiiciently formed to stand such pressure. The difficulty with prior art methods has been that the pressure of thenitrogen has been so lowin the early steps\of the sealing-in process that air has been sucked into the lamp through the opening being sealed and has defeated the purpose of the nitrogen atmosphere. My invention removes this dificulty by providing a suiiicient atmosphere of nitrogen to the interior of the tube during the chamber.

sealing oil process and an increased pressure during the final steps of the seal.

, In Fig. 1, I have illustrated a lathe ID with revolving chuck Illas illustrated holding a `tube I2 therein and a longitudinal moving chuck I3 holding an electrode assembly I4 which is to be inserted in the tube I2 and sealed thereto by means of the flame I5.

` eter than thetube connection to the lamp chuck.

A tube 22 leads from the three-way connection of I8 to the jaws II of the chuck as illustrated in full and dotted lines in Fig. 1. Thev tube 20 must have suicient length to slow up the escaping gas in order to prevent lowering the pressure in the tubing connected to the pressure release If this iiow is fast, as it would be without tube 20 being used, a partial vacuum will be created in tube l22. By impeding the flow through tube I9 by the use of tube 20 of suitable small cross-section and of suicient length, the pressure in tube 22 is maintained high enough tol insure gas flow toward the lamp .chuck and not from it. As an example, I have found that with rubber tubing 20 having an opening 'of Y approximately the same diameter :as the tubing I6 and 22, for example 1% inch, then al length of four to six or more inches of tubing 20 will work satisfactorily. This length can be shortened if the diameter of the opening 2l` -is made smaller. The pressure of the gas and length and diameter of opening of the release tube 2l) is such as to t produce an atmosphere slightly greater than the` outside atmosphere.

As illustrated in Fig. 3, the tube 22 terminates at a central chamber 23 of the chuck which has oil' when not desired as by the clamp 21 holding it against the side of the chuck. A

In orderto illustrate the application in the invention, I have chosen a tube which is rather diilicult to seal by reason of itsv small structure trodes therein. The complete tube, ,except for` and the high temperature which must be applied to each end for the purpose of sealing the electhe closing of the tubulation 29, is illustrated in Fig. 7. This tube comprises a hollow tubular container 'of rather small diameterquartz which is illustrated approximately actual size. This container has a single lead-in electrode Il at one end and a double lead-in electrode 32 at the opposite end. Both the electrodes 3i and 32 must be sealed in the tube under the high temperature necessary to make a seal with the quartz tubing.

30 and have about these electrodes a continuous f but varying pressure of nitrogen or other inert gas to'rorm the seal without any oxidization of the electrode structure that would render them worthless.`

Returning to Fig. 3, I have disclosed the tube 30 having one of its open ends 33 surrounding the opening 24 supplying nitrogen from the central portion of thechuck. 'I'he other chuck has the electrode it secured therein and' this electrode is moved within the end 34 of the tube until the bead of glass about the electrode lead-in is adjacent the tip end 34 f the tube as illustrated in dotted lines.` The tubulation 29 is closed in this instance. The supply from the nitrogen -source is in operation and in.vie'w of the restricted side opening 2i in the pressure release I1, the

nitrogen is applied to the interior of the tube with just suillclent pressure to keep a steady stream flowing past the electrode Il through the open end 34' to prevent any egress of air therein and thus prevent any oxidization of the electrode.

This pressure'is also gentle enough to permit the gradual closing of the seal as disclosed in Figs. 3 and 4. When the seal has been closed', the op'erator applies his ilnger as disclosed in dotted lines at Ii in Figs. 1 and 2,so that the pressure of the nitrogen inside of the tube increases as disclosed by the heavier arrows 38 in Fig. 5 to round out the seal asit coolsat 3l.

The end of thetubulation 29 is then opened i at.. I0' and the tube reversed with its sealed end within the revolving -jaws i I as illustrated in Fig. 6. The side opening 25 and the rubber hose connection 36 to the central chamber 23 of the chuck is then connected to the tubulation 29 to provide the entrance of the nitrogen into the interiorof the tube. The longitudinally moving chuck il then has the tube terminal cathode electrode structure 32 with its bead 4l inserted in the remaining open end 33.` The nitrogen then flows through the tube and out the open end 33 at a gentle .pressure until the seal is closed. The pressure is then increased bf the operator applying his iinger to the restricted opening 2| and the seal rounded out as the seal cools. The quartz 'casing tube is then in the form disclosed in Fig. I

. ing 2i, control the inert atmosphere'toa pressure desired at any particular instance.

I have chosen the particular tube and materials described in order to emphasize the application of my invention to a tube which is difiicult to satisfactoriiy seal. It is apparent, however, that the invention is applicable to various other types of `tubes and that various modifications may be made inthe particular formror apparatus illustrated and the steps described. Accordingly, I

desire only such limitations to be' imposed upon fl the following'ciaims as is necessitated by the prior art.

I claim:

1. Means for sealing a tube comprising a chuck, a gas connection to the central portion within the jaws of said chuck having an open side release with greater impedance to gas ilow than said gas connection.

2. The method of sealing an electrode in-one end of a glass'tube which comprises revolving said tube, applying aninert atmosphere to the interior .pf' the tube `while revolving, Vreleasing `the inert atmosphere only to the extent that the pressure applied to the interiorA of the tube does not interfere with the sealing process and yet is sufiicient to prevent any outside atmosphere entering the tube, inserting an electrode in the inert atmosphere flowing from the open end oi'.' the tube, applying heat thereto and sealing the end ofAthe tube about said electrode, and stopping the release of said inert atmosphere while the seal is still molten to round out the tube around the electrode.

GEORGE A. FREEMAN. 

